Fibrous structures

ABSTRACT

Thins invention relates to a fibrous structure constituted as least in part by so-called annular fibres in the form of a closed loop and said annular fibres are mixed with so called linear fibres having free ends.

United States Patent O 3,823,059 FIBROUS STRUCTURES Guy J. Jacquelin, Grenoble, France, assgnor to Novipro, Grenoble, France Filed July 13, 1972, Ser. No. 271,227 Claims priority, appli7ca11ig16i0'rance, July 1S, 1971,

Int. 'CL B28b 23/04; B32!) 13/02, 13/14 U.S. Cl. 161-150 3 Claims ABSTRACT F THE DISCLOSURE This invention relates to a fibrous structure constituted at least in part by so-called annular fibres in the form of a closed loop and said annular fibres are mixed with socalled linear fibres having free ends.

The present invention relates to fibrous structures whose component lfibres are distributed in any manner, on the one hand for multiplying their points of contact and ensuring a cohesion by their intermediary, and on the other hand for conferring a certain isotropy to the properties of this cohesion.

The invention relates more especially to the fibrous structures in the form of sheets, in which the fibres extend parallel to a common plane.

Up to the present day, such sheets are obtained from so-called linear fibres, i.e. fibres whose ends are free. Their methods of manufacture use textile techniques (carding, etc.) or paper-making techniques using water aS vector for distributing the fibres in a sheet.

During their transport in a fluid, the linear fibres which are moreover more or less supple sweep relatively large volumes in their movements. Their ends frequently catch in one another and thus tend to form flocks. 'Ihese docks, when there are any, harm the quality of the sheet and this is why every effort is made, although not always with success, to disaggregate them.

Furthermore, the distribution of the linear fibres is not as regular as would be desired in order to obtain the sought after isotropy. The mechanical resistance of the sheets thus manufactured is therefore limited.

The invention has for its object to remedy these disadvantages. In fact, the probabiility of mutual catching of Athe fibres is considerably reduced, with the result that the formation of flocks becomes very random. In addition, the sheets formed are much more regular and their properties much closer to the theoretical isotropy; in particular, their mechanical resistance is increased. IFurthermore, the cohesion is improved since it no longer results only from the size of the interfibre contact surface, but also from the fact that these fibres have no free end any more.

In accordance with the invention, the fibrous structure is constituted at least in part by so-called annular bres, i.e. inthe form of a closed loop.

` The accompanying drawings will enable the invention to be more readily understood and other characteristics and advantages thereof to be shown.

In the drawings,

FIG. 1 is a perspective view showing a fibrous sheet,

FIG. 2 is a plan view of an enlargment of part of the sheet designated by arrow -F of FIG. l, this view illustrating the structure obtained from linear libres,

IFIG. 3 is a view similar to FIG. 2, showing the structure obtained according to the invention from annular fibres.

As shown in FIG. 2, the known structures are made by treating linear fibres 1, i.e. fibres whose ends are free. These fibres are substantially parallel to the plane of the sheet 2 (FIG. 1) but they are disposed so that their orientaice tions are multiple, their distribution effected at random and being of any conformation: straight, concave, winding, etc.; thanks to this, they are in contact with one another at numerous points, this resultsing in a cohesion.

According to the invention, and as shown in FIG. 3, the structure is obtained from annular fibres 3, i.e. fibres having no end. They therefore look like closed loops whose contour may take any shape; circular, oval, ligure of eight, etc. They may be assimilated to linear fibres whose ends would be connected.

At an equal developed length, the bulk volume of the annular fibres 3 is smaller than that of the linear fibres 1. In addition, the probability of catching of the annular fibres is considerably reduced with respect to that of the linear libres 1, since the ends of these latter are free.

Therefore, the lbehaviour of these annular fibres, when they are in suspension, is much better for their depositing in a layer and leads to a greater homogeneity. Consequently, the fibrous sheets obtained (FIG. 3) are much more regular and their resistance is improved.

In addition, since, at an equal developed length, the annular fibre appears to behave like a linear fibre Whose ends would be connected, with an equal interfibre contact surface, the connection of the annular fibres is more sure than that of the linear fibres. In fact, if all the so-called secondary annular fibres are considered to be connected to the same so-called principal annular fibre, the stresses may be transmitted by the contact zones of any secondary fibre to any other secondary fibre, along the whole of the closed loop constituted by the principal fibre. Under these circumstances, the fibrous sheet obtained has a supplementary cohesion.

The annular fibres 3 preferably have a loop diameter of less than 5 cm.

In addition, it is obvious that the fibrous structure may combine annular fibres with linear fibres.

An example of manufacture of a fibrous structure according to the invention is given hereinafter by Way of non-limiting example.

A polypropylene tube having a diameter of 20 mm. and a wall thickness of 50 microns is made by extrusionblowing. The annular fibres are obtained by transverse sectioning of this tube at a pitch of 0.5 mm. These fibres therefore have a rectangular section of 50 microns by 500 microns.

They are then dispersed in a fluid at a concentration of 0.5 gram per litre. The suspension is lfiltered in conventional manner for small paper-making moulds. A fibrous structure is thus obtained which may be consolidated by heat treatment or addition of a binding agent.

The fibrous structure of the invention may be used in all cases where fibres are not to catch in one another during manufacture, as Well as in all cases where the resistance and cohesion are to be improved.

It is applicable to the manufacture of special papers and sheets of the non-Woven type with multiple uses: textiles, sheets, wall coatings, etc.

What is claimed is:

1. A non-woven fibrous structure comprising a multiplicity of annular fibres lying substantially in planes which are generally parallel to a surface of the structure and distributed throughout the structure with portions of a multiplicity of the fibres overlapping and contacting others of the fibres, each of said fibres being re-entrant and in the form of a closed loop without extensions of the fibre outside of the loop.

2. A non-woven fibrous structure as set forth in claim 1, further comprising a plurality of linear fibres having free ends interspersed with and contacting a plurality of said annular fibres.

3 4 3. An non-woven fibrous structure as set forth in claim 3,63 9,197 2/1972 Spain 161--42 X 1, wherein said structure is a sheet which is thin relative 3,022,210 2/ 1962 Philipps 161-170 X to the dimensions of its surfaces, and wherein the diam- 3,013,915 12/ 1961 Morgan 161-170 X eter of the annular fibres is less than 5 centimeters.

MARION MCCAMISH, Primary Examiner U.S. Cl. X.R.

3,348,993 10/1967 sissons 161-17ox 161-155 156 157 169 170 173 3,637,457 1/1972 Gothard et a1 161-170X 

